Skip glitchy search animation

* Entering and leaving search now takes effect right away.
* Should fix race in which tapping an app while search results are
  loading causes a tap on the previous app in the position, rather
  than on the search result.
* Helps prevent the scrollbar from appearing to be scrolled down
  somewhat when leaving search with floating header rows present;
  still happens sometimes, though (on stock OS launcher, too).

Issue: calyxos#1413
Change-Id: I67bc59456eb2e57e13b1b99509d3313ff0243b88